Speaker
Description
In metallurgy, gas is often injected into melts for mixing, degassing or refining. The knowledge of the two-phase flow behaviour is of utmost relevance for optimisation and process control. However, the measurement of the flow structure, the gas distribution and the characteristics of the bubbles is very challenging, because of the opaqueness and the high temperature of industrial relevant melts. Although numerical models have significantly improved recently, it is indispensable to validate the simulation results with experimental data.
A new experimental facility has been designed and recently commissioned at Helmholtz-Zentrum Dresden - Rossendorf for systematic investigation of bubble plumes in liquid Sn‑40wt%Bi at 200 °C. The thermophysical properties of this alloy are very similar to those of steel. The experiment is a 1:5.25 model of an industrial ladle and consists of a cylindrical vessel with inner diameter of 600 mm, which is filled with 1.7 tons of SnBi. Gas can be injected at the bottom of the vessel at four different locations, which can be equipped with different plug types. Furthermore, low-pressure conditions for modelling VOD (Vacuum Oxygen Decarburization) application can be achieved by the use of a vacuum pump.
The gas distribution was measured by an array of 64 resistive probes arranged in a rectangular grid with a spacing of 10 mm and a time resolution of 1 kHz. This technique allows also the determination of bubble properties like bubble speed and diameter. The velocity of the liquid was measured by Ultrasound Doppler Velocimetry. The paper provides a description of the new setup in detail and presents measurement results characterizing the bubbly flow for varying gas flow rates and different configurations for gas injection.